Inductive Power Transfer Control for LCL Pick-up
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Solution Overview
Problem
In inductive power transfer systems, the transient inrush power drawn by pick-ups during normal power regulation causes a disturbance in track current, limiting power flow to other pick-ups, and existing control methods are not applicable to series-parallel tuned LCL pick-up topologies due to the requirement of a large DC inductor for continuous current conduction.
Innovation Solution
A control method and circuit that selectively shunts diodes in a diode bridge to recirculate AC current to the resonant circuit during predetermined periods of the AC current, synchronizing with the AC current to minimize track current transient disturbances, using switches in parallel with the diodes to control the recirculation and rectification of AC current, allowing for smooth power regulation and transition between fully on and fully off states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If slow switching control method is used in LCL pick-up, then power regulation is achieved, but transient inrush power causes track current disturbance
Solution Approach 1:
The control circuit initiates a soft-start sequence that gradually increases the duty cycle from zero to the target value over a predetermined time period. This preliminary gradual activation prevents sudden inrush current by building up power transfer incrementally, thereby avoiding track current disturbance while achieving the desired power regulation level.
2Object-generated harmful factors
If simple parallel LC tuned pick-up controller is used, then track current transient disturbance is minimized, but it cannot be used in LCL topology
Solution Approach 1:
The control circuit modifies the duty cycle parameter of the switching element to regulate power transfer. By dynamically adjusting this single parameter, the system achieves smooth power transitions and minimizes transient disturbances in the LCL topology without requiring additional circuit components, thus adapting the simple control approach to the complex LCL configuration.
3Stability of the object's composition
If large DC inductor is used for continuous current conduction, then current continuity is achieved, but device complexity and size increase
Solution Approach 1:
The invention extracts and eliminates the large DC inductor component from the LCL pick-up circuit by implementing a control strategy that achieves smooth current transitions through duty cycle modulation. This removal simplifies the circuit topology, reduces component count and size, while maintaining current continuity through controlled soft-start and soft-stop sequences.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes track current transient disturbances, enabling smooth power transition and efficient power regulation in series-parallel tuned LCL pick-up systems, maintaining high efficiency and reducing the impact on other pick-ups, while accommodating variations in mutual coupling and load conditions.
Implementation Method 1
a resonant circuit consisting of at least a pick-up coil and a tuning capacitor
Implementation Method 2
power is transferred inductively between a primary conductive path or track supplied by an alternating-current power supply
Implementation Method 3
a diode bridge adapted to rectify an AC current from the resonant circuit and supply a DC current to a DC output
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An inductive power transfer (IPT) control method is disclosed for controlling the output of an IPT pick-up. The invention involves selectively shunting first and second diodes of a diode bridge to selectively rectify an AC current input for supply to a load, or recirculate the AC current to a resonant circuit coupled to the input of the controller. By controlling the proportion of each positive-negative cycle of the AC input which is rectified/recirculated, the output is regulated. Also disclosed is an IPT controller adapted to perform the method, an IPT pick-up incorporating the IPT controller, and an IPT system incorporating at least one such IPT pick-up.